Shock absorber



Nov. 2l, 1950 c. E. TACK ETAL SHOCK ABSORBER Filed June 30, 1944 INVENTORS AZI.,

Patented Nov. 21, 1950 SHOCK ABSORBER Earl E. Tack and Fred E. Eachman, Chicago, Ill., assignors to American Steel Foundries, Chicago, Ill., a corporation of New Jersey Application .lune 30, 1944, Serial No. 543,02)

2 Claims. (Cl. 257-454) Our invention relates to shock absorbers and more particularly to an hydraulic device commonly called an oleo strut, such device being adapted for utilization particularly in the connection between the landing gear and fuselage of aircraft.

The primary object of our invention is to design a strut such as above described, wherein a compressed gas spring is provided for the purpose of urging the strut to its normal extended position after compression or closure thereof, said gas spring being spaced from the hydraulic fluid within the device to prevent foaming of said fluid.

Another object of our invention is to provide a novel hollow piston rod carried by the strut cylinder and reciprocal within the hollow piston, said rod carrying a piston head at its inner end comprising means for metering the hydraulic fluid within the hollow piston.

In our novel arrangement the piston rod isprovided with an axial passage to permit lling of the internal piston chamber with hydraulic iiuid without disassemblingthe strut, said passageway being closed by means of a cap threaded on the outer extremity of the piston rod.

In the drawings, Figure 1 is a sectional View taken in a plane bisecting our novel structure substantially on the longitudinal axis thereof, the left half of this ligure showing the strut in its extended position andthe right half of this figure showing the strut in its closed or compressed position.

Figure 2 is a sectional view taken in the radial plane indicated by the line 2-2 of Figure 1.

Figures 3 to 5, inclusive, illustrate various elements of the metering valve assembly carried by the piston head, Figure 3 being a plan view of the spring washer, Figure 4 being a plan view of the resilient valve plate, and Figure 5 being az plan view of the valve spring.

Figure 6 is an enlarged sectional view showing in detail the reservoir valve illustrated in Figure l; and Figures 7 8 plan views, respectively, of the valve plate and the valve spring utilized in the reservoir valve.

Describing our invention in detail, my novel structure comprises a top follower in the form of a cylinder 2 with a bracket affording convenient connection to the fuselage of an associated aircraft (not shown). A hollow piston ii reciprocates within the cylinder 2 against the resilient resistance of a compressed gas spring consisting of a quantity of compressed gas, such', as air, which is forced into the .cylinder 2 through a fitting a. The piston s is afforded a sndable gas-tight t Within the cylinder 2 by means of an annular packing gland l0 and an annular bearing I2 received within a collar I4 secured to the lower extremity of the cylinder 2, as by welding at I6. The bearing l2 is compressed against the gland I0 by means of a packing gland nut I8 threaded engagement as at 20 with the sleeve The piston 6 is a hollow member comprising a piston head 22 and radially inner and outer hydraulic fluid chambers 24 and 26 separated by the annular wall 2S, the outer annular chamber 2E functioning as a reservoir to collect leakage fluid and return the same to the main chamber 24, as hereinafter more particularly described, tlrough the reservoir valve generally designated 3 The cylinder 2 carries a hollow piston rod 32, which extends at its upper extremity through an opening 33 in the top Wall or head 35 of the cylinder, said rod being in shouldered engagement at 3l with a gasket 39 affording a gas-tight seal for the opening 33. The upper extremity of the rod is threaded as at 4I' for engagement with a threaded Vcap 43, vwhich is seated against a gasket 45 and is operable to draw the rod 32 into tight engagement with the gasket 39.

Adjacent its lower extremity, the rod 32 carries the piston head Sli slidably engaging the wall 28 as at 36, said head SliA comprising valvemeans for metering hydraulic fluid within the chamber 24, as hereinafter more particularly described.A

The piston head valve means comprises a plurality of radially inner ports 38, 38 and a plurality of radially outer ports di), 4U. As will be understood from a consideration of Figure 2the ports 38, 38 are eight in number, and the upperv ein tremities of four of these ports are closed by the resilient valve plate 42, which comprises the central opening 4l for the reception of the rod 32. Av plurality of annular spring washers lill, i4 are interposed between the resilient valve plate 42 and a shoulder d6 adjacent the lower extremity of the rod 32.

The lower extremities of the ports 4D, 40 are closed bya resilient valve plate (i8V comprising slots 5t, 5i! registering with the lower extremities of the ports 38, 38, and the valve plate 48 is resiliently urged to its closed position by means of a spring 52 and a washer 54'.;

The spring 52, asbest seen in Figure 5, is a somewhat star-shaped resilient disc comprising a plurality of prongs 54, 54 for engagement withV the plate 48, and theldisc 52 also comprises a Entral opening 56 for the reception of the piston rod 32. A nut 58 is threaded on the lower end of the rod 32 and is operable to urge the piston head 34 and the above-mentioned valve elements into a pile against the shoulder 46 of the rod 32.

The piston rod 32 reciprocates within an opening 60 through the piston head 22 and is afforded a gas-tight slidable fit therewith by means of the oil ring 62; and the piston head 22 is provided with an annular groove 64 communicating by means of ports 66, 66 with the reservoir chamber 26. Thus, any leakage oil from the chamber 24 collects in the groove 64 and is conveyed by means of the ports 66, 66 to the reservoir chamber 26 from which it passes into-ports or passages 68, 68 in the bottom wall 10 of the piston.

The oil from the reservoir chamber 26 collects in a well or chamber 12 from which it is returned to the chamber 24 by means of the reservoir valve 30. The valve 30 is illustrated in detail in Figures 6 1 to 8 and includes an annular base plate 14 recessed in the wall 'l0 ofthe piston., said base plate comprising a plurality of. ports l, '|62 closed by means of a plurality offspring Washers T8', 1:8- and the. base plate 1'4 comprises thea central Dort or passage 80 closed byl means, of a valve plate 82, whichis resiliently urged to its closed' position.

by means. ofaspring 84 bearing; against the, valve. cap 86, which is threaded at 88 into the wall of the: piston to maintain the variousv el ments of the reservoir valve 30= in normal assembled relationsl'xip. The,- valve plate 82 is. shown in detail in Figure?, from.- Wllich it will: be seenthat: said. plate is a'. round rigid rnen'lberA with a plurality of; portsl 8.0, 90; registered with the beforementioned ports. 1:6', 7.6i through the.` base plate 2.4.

The spring 84.\ isy anannular` disc-like mem-bei:`

comprising a plurality of prongs or projections 92, 92 extending toward the, center of' the member 84 and defining therebetween slots 94, 98a permitting hydraulic fluid tu. pass. therethrough and the cap 86 is provided with a plurality.y of ports 96, 96.

Thus, it will be understood that: en` the: compression or closure stroke of our novel strut, asA ,L seen in the right half' of Figure l, hydraulic. fluid;

is. metered through they four ports 38:', 38 which; are not closed by the resilient. valve plate 4.2i Under certain conditions wherein the structure is moved rapidly to` its closed position, hydraulic.

pressure in the other four ports 38, 38. exesf the valve plate 42 to'- its open position, thus admitting the hydraulic fluid through all' eight of'4 the ports 38, 38 as the. strut is compressed.

On the release or extension stroke of the strut, the hydraulic uid within the chamber 24 is metered through the ports 40, 40 by urging te resilient valve plate 48- to itsI open positionagainst the resistance ofv theY spring 52"; and it may be noted at this point that the upper extremity of the piston head 34 is formed with an upstanding` annularflange or projection 98 with atapered upper extremity |66-, which is received within the tapered' annular dashpot chamber H12 formed by' the piston wall 28 and the depending boss` |64` integrally formed with the piston headi 22. rI hus, as the tapered extremity |00 of the flange 98 enters the annular chamber |02,r hydraulic fluid' is metered from saidv chamber to effect additional dam-pening of the extension stroke of' the piston at the extremity of saldi stroke.

It will be understood that on the closure stroke of the strut some of the; hydraulic' fluid within the chamber 24 is metered tl'iroughk theports T6,

'[6 and 90, 90 of the reservoir# valve 30 against' the resilient resistance of the spring washer 18, 18, and on the extension stroke of the strut, the hydraulic fluid Within the well 72 passes upwardly through the port 80, the ports 90, and the ports 96, 96 into the chamber 24 against the resistance of the spring 84.

Inasmuch as the spring 84 is relatively weak withA respect to the spring, Washer 18', 18, fluid within the well T2 may pass into the chamber 24 against less resistance than that encountered on the closure stroke of the device when some fluid Within the chamber 24 is forced into the chamber 72 through the valve 3|), as above described. Becauseof this arrangement, surplus fiud within the reservoir chamber 26 is constantly circulated through the valve 30 into the chamber 24, thus restoring to said chamber 24 any leakage fluid which escapes therefrom through .the annular groove 64 in the piston head 22.

As mentioned above, the rod 32 is a hollow member comprisingv a central axial' passage |06 extending from end to end thereof, said. passage4 communicating with the portion of the chamber 24 above the piston. head 34 by means' of one or more ports. |08, |08. By this. arrangement, the chamber 24 may be lled with hydraulic fluid through the passage |06 when the strut is in its extended position, as seen. the left half of Figure 1. Thereafter the cap.43 may be threaded on the rod 32 andthe strut may. be urged; tocompressed' or closed position., as seen in the iight half of Figure 1, thereby partiallyv filling' the reservoir chamber 26, whereupon the capll|3- may be removed and the upper extremity of the chamber 24 may be completely lled with hydraulic fluid through the passage |06 and the ports |082 Bymeans of this novel arrangement, the strut may bel filledy withv hydraulic fluid after the' various parts have beenassembled.

It will be noted that the'resiient discs 44, 4'4' are dsposed immediately beneathy the radial passages |08, |08. The discs 44 are-flexible away fromv the punger head 34 and inasmuch as they are disposed immediately adjacent toA the passagewa-ys ports |08 the fluid flowing through these passageways on closure of the strut will ow over the end disc or spring washer 44' and thus resist openingof valve plate 4-2. This feature also prevents fluttering of the spring washersV and thus eliminates not only erratic action of the shock absorber but also reduces exure ofi the spring washers 44' thereby greatly prolonging their life.. It will be appreciated that this action is possible only because of the immediate. proximity of the openings |08 to the washers 44 as mayv be readily seen in Figure 1.

It may also be noted that the gas spring within the cylinder 2 is at all times spaced from the hydraulic fluid within the hollow piston 6, thus preventing foaming of thel hydraulic fiuid as' it is metered during actuation of the device.

It is to be understood that we do not wish. to be limited by the exact embodiment of the device shown which is merely by way of illustration and not limitation as various and other forms ofthe device will, of course, be apparent to those skiled in the art without` departing from the spirit of the invention or the scope ofy the claims.

We claim:A

1. Inv an hydraulic shock strut, a cylindrical followera hollow'piston reciprocal therewithin', a plungerV tube, connectedy to the follower' and arranged coaxial therewith and extending through the head of saidv piston and, in fluid tight engagementv therewith, saidJ piston having a cylindricaly chamber receiving said plunger tube therein, a

of the strut, said valve means comprising a plate and a plurality of spring washers disposed within said one portion of said piston chamber, said plate being adapted to seat against said plunger head to close the ports and said washers being ar-f ranged in a pile in shouldered engagement with the tube and reacting against said plate for urging said plate against said plunger head to the closed position thereof, passage means through said tube communicating with the other portion of said piston chamber, and radial passageways through said tube communicating with said passage means and with said one portion of said piston chamber, said piston chamber, passage means and passageways having all of the available spaces lled with fiuid, said passageways being disposed immediately adjacent the end Washer of the pile remote from the plate, said fluid during closure of said strut being accommodated flow from said other portion of said piston chamber to said one portion thereof through said passage means and passageways and co-incidentally vthrough said ports by unseating said plate and flexing said washers, said luid during closure of said strut issuing across the end washer and thus resisting flexure of said washers and opening of csaid valve means, and a gas spring acting between said follower and piston.

2. In an hydraulic shock absorber, a cylindrical member closed at opposite ends, a plunger comprising a tube extending through one end of said member, said member having a cylindrical chamber therein, a head carried by said tube for reciprocation within said chamber, said head dividing said chamber into two axially spaced portions, metering valve means within one portion of said chamber between said head and said one end of said member, by-pass Valve means within the other portion of said chamber, said valve means being carried by said tube, said metering valve means comprising ports through the head, a passage through said tube communicating with the other portion of said chamber, a plate Within said one portion sleeved on said tube, resilient discs reacting between said plate and said tube for closing said ports, radial passageways through said tube communicating with said one portion of said chamber and with said passage, said chamber, passage and passageways being filled with hydraulic uid, said metering means being adapted to open said ports during closure of said strut by unseating of said plate against the exure of said discs, the fiexure of said discs and opening of said ports being resisted vby fluid flowing through said passageways against said discs.

CARL E. TACK. FRED E. BACHMAN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,291,016 Kellogg Jan. 14, 1919 1,918,697 Gruss July 18, 1933 2,057,893 Gross Oct. 20, 1936 2,078,364 Becker et al. Apr. 27, 1937 2,089,656 Magrum Aug. 10, 1937 2,138,513 Rossman et al Nov. 29, 1938 FOREIGN PATENTS Number Country Date 452,895 Great Britain Sept. 1, 1936 496,059 Great Britain Nov. 24, 1938 359,228 Italy May 16, 1938 

